Pumps capable of use as heart pumps and blood pumps

ABSTRACT

Pumps and pumping methods wherein rotators having radial extent cause propulsion of the pumped fluid and wherein the rotators are outwardly convergent one toward another whereby the product, fluid volume times fluid velocity, at each radial location is substantially constant. The pumps are capable of use as heart pumps, blood pumps, and as pumps to pump all types of natural or artificial biological fluids in connnection with the maintenance of life and/or biological functions in a human body, animal body, or any other pumping function. The pumps can be used to replace or assist the pumping functions of the heart in vivo or ex vivo. The pumps can be used to pump biological fluids in vitro or in any in vivo, ex vivo, and in vitro combination. The pumps may be also used to pump natural or artificial biological fluids as well as nonbiological fluids. The nonbiological fluids so pumped may be pumped in connection with biological or nonbiological activities, functions, and/or applications.

United States Patent 1191 1111 3,864,055

Kletschka et al. Feb. 4, 1975 [54] PUMPS CAPABLE OF USE AS HEART 361,2096/1938 Italy 415/90 PS N LOO PUMPS 331,142 6/l930 Great Britain. 415/90599,519 10/1932 Germany 415/90 [76] Inventors: Harold D. Kletschka, 1925Noble Dr., Minneapolis, Minn. 55422; Edson Rafferty BOX 479, PrimaryExaminer-Henry F. Raduazo Excelsior Mlnn- 55331 Attorney, Agent, orFirm-Carl B. Fox, Jr. [22] Filed: Nov. 9, 1973 [21] Appl. No.: 414,225

Related U.S. Application Data [57] ABSTRACT [63] Continuation-in-part ofSer. No. 204,980, Dec. 6,

1971, abandoned, which is a continuation-in-part of Pumps and pumpmgmethods wherem rotators havmg s 33 ,137,9 1 19 9 PM 3, 47,324 radialextent cause propulsion of the pumped fluid and which is acontinuation-in-part of Ser. No. 678,265, wherein the rotators areoutwardly convergent one to- Oct. 26, 1967, Pat. No. 3,487,784. wardanother whereby the product, fluid volume times fluid velocity, at eachradial location is substantially [52] U.S. Cl 415/1, 415/90, 415/DIG. 4,constant, The pumps are capable of use as heart 128/214 416/186 pumps,blood pumps, and as pumps to pump all types Illl- F0411 F04d 29/26 ofnatural or artificial biological fluids in connnection Field of Search.415/215, 9 with the maintenance of life and/or biological func- 415/28/2 R tions in a human body, animal body, or any other pumpingfunction. The pumps can be used to replace [56] Re e ces C ted or assistthe pumping functions of the heart in vivo or UNITED STATES PATENTS exvivo. The pumps can be used to pump biological 748,294 12/1903 MacKenzie415/170 A fluids V1119 01 any in vivo, ex vivo and 940,103 11/1909 Feld415/90 combination- The Pumps y be also used 10 P 1,715,944 6/1929Oliver 415/170 A natural or artificial biological fluids as well asnonbio- 2,087,834 6/1937 Brown ct a1. 415/90 logical fluids. Thenonbiological fluids so pumped may 2,8 6,769 3/1959 Cordovu G- 4 bepumped in connection with biological or nonbio- 3l39-832 7/1964 Saunders4l5/DIG- 4 logical activities, functions, and/or applications.

FOREIGN PATENTS OR APPLICATIONS 4/1948 Canada 415/215 12 Claims, 10Drawing Figures PATENTED FEB 4 I 75 SHEEI 1 OF 5 PATENIEI] FEB M975PUMPS CAPABLE OF USE AS HEART PUMPS AND BLOOD PUMPS This application isa continuation-in-part of application Ser. No. 204,980, filed Dec. 6,1971, now abandoned which was a continuation-in-part of application Ser.No. 886,137, filed Dec. 18, 1969, now U.S. Pat. No. 3,647,324, which inturn is a continuation-in-part of application Ser. No. 678,265, filedOct. 26, 1967, now U.S. Pat. No. 3,487,784.

BACKGROUND OF THE INVENTION 1. Field of the Invention The field of theinvention is the field relating to pumping apparatuses, particularly toapparatus useful for pumping blood of a living person, or ofa livinganimal, to replace one or more pumping functions of the human or animalheart in case of disability thereof. The heart replacement may bepartial or complete, temporary or permanent. While the pumps providedaccording to the invention are provided principally for pumping blood,the pumps may be employed in other instances for pumping othermaterials. The pumping equipment provided by the invention has fluidaccelerators or rotators which rotate to impel the fluid circularly atsubstantially the speed of the rotators. The pumps are adapted forpumping of blood, and other delicate fluid materials, biological andnonbiological in nature, without any pronounced physical effect on theblood or other fluid being pumped. The pumps do not impose suddenpressure changes, impacts, rapid changes in direction of flow, in orderto prevent injury to or destruction of the pumped material and itscomponents.

In the case where blood and similar liquids have been pumped, artificialheart pumps generally have been of the positive displacement type.Because of the relatively delicate nature and structure of blood, it hasbeen found that use of centrifugal pumps invariably results in physicaldisruption of the blood and at least some of its components. Although apulsating movement of blood through the body may not be necessary tosustain life, the prior art has not afforded a solution to the problemsinvolved in utilization of centrifugal pumps for pumping blood, since atleast partial destruc tion of blood has always resulted when centrifugalpumps were used. This invention solves these problems, by providingrotative pumping means for pumping blood or other delicate fluids, whichproduce minimum levels of shear and tubulence thus limiting anysignificant destruction of the fluid and its components resulting fromthe pumping.

2. Summary of the Invention The invention is of rotative pumps which aresuitable for use as heart pumps, blood pumps, and as pumps to pump alltypes of natural or artificial biological fluids in connection with themaintenance of life and/or biological functions in a human body, animalbody, or any other pumping function. The pumps can be used to replace orassist the pumping functions of the heart in vivo or ex vivo. The pumpscan be used to pump biological fluids in vitro or in any in vivo, exvivo, and in vitro combination. The pumps may also be used to pump Thepumps according to the invention are rotative pumps having rotatorsthrough passages of which the fluid flows outwardly from the axis of therotator. The rotating rotator surfaces cause the fluid, introduced at ornear the rotator axis, to move substantially circularly around therotator axis at continuously increasing speed as the fluid moves outwardtoward the rotator periphery. The fluid circulates substantially withthe rotator at relatively constant rotational speeds (revolutions perminute) as it moves outwardly, so that its linear speed (distance/time)continuously increases as the fluid moves outwardly in continuouslyenlarging circular paths. The fluid moves circularly at approximatelythe angular velocity of the rotator, and this velocity increases as theradial distance from the axis increases. In order that the volume flowremains approximately constant past all radial distances from the fluidinlet to the rotator periphery, the rotator passages (spacing betweenrotators) decrease in size as the inverse function of the radialdistance from the rotator axis. This prevents effects on the fluid suchas cavitation, pressurization, depressurization, and the like, fromoccuring inside the pumps, thereby preventing shock and damage to thefluid being pumped.

The pumps may be used in pumping blood for circulation through the bodypassages, veins, arteries, etc., of a living person or animal, or forpumping blood through artificial kidneys and lungs of a person oranimal. The pumps are adaptable for use disposed within a body cavity,as replacements for any or all of the pumping functions of the heart.The pumps herein provided may also be used externally of the body forpumping blood into the body of a person or animal. The pumps are adaptedto pump without producing severe pressure changes, physical impacts, andthe like, so that none of the blood or other fluid components aresubjected to treatment which will destroy them for use. The pumps do notrequire the use of valves, such as those of the heart, but valves may beprovided if desired particularly in heart assist-type usage.

The punps are useful in both biological and nonbiological applications.The pumps could, for example, be used to propel a motorboat, the pumpsbeing very quiet and of low turbulence, in centrifuging apparatus, asinfusion pumps, as suction pumps (for chest tubes, for example), asaspiration devices (to suction out blood from the operative field in anautraumatic fashion so that the blood might be reused in order to saveon blood transfusions, etc.) to pump water from boats, for fountainsprays and garden waterfalls, for pumping slurries such as sewage, andfor many other uses including but not restricted to uses where gentlehandling of the fluid may be desired.

BRIEF DESCRIPTIONS OF THE DRAWINGS FIGS. 1-2 are vertical crosssectional views of a pump of preferred form according to the invention,FIG. 1 being taken along the axes of rotation of the pump rotators, andFIG. 2 being taken transverse thereto.

FIGS. 3-4 are cross sectional views of a pump of modified form accordingto the invention, FIG. 3 being taken along the axes of rotation of thepump rotators, and FIG. 4 being taken along a spherical surface be tweenthe rotators.

FIGS. 5-6 are similar to FIGS. 1 and 3, and show additional modifiedembodiments of apparatuses according to the invention.

FIG. 7 is a cross sectional view of an additional form of rotator usefulin connection with the invention.

FIGS. 8-10 are similar to FIG. I, and show additional modifiedembodiments of apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pumps will be'describedwith blood as the fluid being pumped, since that is the primary purposefor which the pumps according to the invention have been developed, butit is to be understood that the'pumps will be useful for all of the usesand purposes mentioned-in the disclosure, and the description may beapplied to such uses and purposes.

Blood is a complex and delicate fluid. It is essentially made up ofplasma, a pale yellow liquid containing microscopic materials and theformed elements which include the red corpuscles (erythrocytes), whitecorpuscles (leukocytes), and platelets (thrombocytes). These and theother constituents of blood, as well as the nature of suspension ofthese materials in blood, are fairly readily affected by the manner inwhich blood is physically handled or treated. Blood subjected tomechanical shear, to impact, to depressurization, or other forces, maybe seriously damaged. In addition the balance between the bloodconstituents may readily be affected. Commencement of deterioration mayresult from physical mishandling of blood. Blood which has been damagedmay be unfit for use.

The heart propels or pumps blood through the body in a circulating,cyclic, fashion. The blood passes repeatedly through the heart. A pumpfor replacing one or more pumping functions of the heart shouldtherefore be capable of repeatedly pumping the same blood, time and timeagain, without damaging theblood, at least not more than to the extentwhere the body can function to repair or replace the blood componentsand eliminate damaged and waste materials therefrom.

Blood also contains dissolved and chemically combined gases, which maybe seriously affected by improper physical handling of the blood. Ithas, for example, been established that subjecting blood to negative orsub-atmospheric pressures of, say, minus 300 millimeters of mercury, isdetrimental not only to the blood cells, which may rupture, but to thebody due to the release of dissolved gases from solution, even when thereduced pressures are only temporary.

The blood pressure is the pressure of the blood on the walls of thearteries, and is dependent on the energy of the heart action, theelasticity of the walls of the arteries the peripheral resistance in thecapillaries, and the volume and viscosity of the blood. The maximumpressure occurs at the time of the systole of the left ventricle of theheart and is termed maximum or systolic pressure. The normal systolicpressure may be from about 80 millimeters of mercury (mm. Hg) to aboutI50 mm. Hg. the pressure ordinarily increasing with increasing age.Pressures somewhat outside this range are not uncommon. The minimumpressure is felt at the diastole of the ventricle and is termed minimumor diastolic pressure. The diastolic pressure is usually about 30 to 50mm. Hg lower than the systolic pressure.

The preferred embodiments of the invention shown and described have incommon that the blood or other fluid is handled gently, without shear,shock, vibration, impact, severe pressure or temperature change. or any5 other condition or treatment which would unduly damage the blood orother fluid. Essentially nonturbulent flow is maintained through thepumps, and the pumped fluid is accelerated gradually and smoothly.

The pumping action obtained may be described as radially increasingpressure gradient pumping, or in some cases more specifically asconstrained forcevortex radially increasing pressure gradient pumping.In centrifugal pumps, the fluid acted on by the vanes of the impeller ispositively driven or thrown outwardly (radially) by the vane rotation.The fluid as it moves from the vanes to the ring-shaped volute spacebeyond the tips of the vanes is reduced in velocity, and as the velocitydecreases the pressure increases according to Bernoulli's theorum.Handling of many delicate fluids, such as blood, in this fashion woulddestroy them for use.

On the other hand, in the pumps provided according to this invention,the pumped fluid is not driven or thrust outwardly but instead isconstrained to circulate in the pumping chamber at increasing speeds asit moves farther and farther from the center. At the outer periphery ofthe accelerator or rotator, the speed of the fluid is maximum.

The action of the fluid in the pumps may be clarified by analogy to aglass of water turning about its vertical axis without sideways motionor wobble. Because of its contact with the sides and the inherentpotential shear force of the water in the glass, the water will rotatein the form of a force-vortex, without much slip or shear betweenradially adjacent particles of water, and the water radially away fromthe center of rotation will be moving faster than water nearer thecenter. If water is introduced through a tube at the axis of the glassand water is removed through one or more holes through the side of theglass and the water in the glass is constrained by capping off the topof the glass, water will be pumped by the rotation of the glass. In thepumps afforded by this invention, while rotators are provided, in anumber of different forms, the rotators are designed such that they actto increase the swirling speed of the liquid passing through the pump,but do not act to drive or throw the liquid toward the periphery orvolute of the pump chamber, but instead only increase the rotationalspeed of the liquid. As the rotative speed of the liquid is increased,it achieves a higher orbit about the center of the accelerator and movestoward the periphery of the chamber.

Referring first to FIGS. 1-2 of the drawings, the pump impeller iscomprised of a pair of non-parallel rotators l6, 17, disposed withinhousing 19 having opposite side walls 20, 21 which are parallel with butspaced from the rotators l6, 17, respectively. The housing continuesradially outwardly to form around the outer edges of the rotators anannular chamber 23. Wall 21 is secured around its edges by screws 21a.

A tubular shaft 24 rotatively disposed through O-ring 25 carries therotators l6, l7. Tubular shaft 24 has opposite circular openings 27, 28providing for passage of fluid incoming through the tubular shaft to thespace between the rotators. Housing 19 has a tubular concentric nippleformation 29, O-ring seal 25 being disposed in suitable ring grooves atthe outside of tubular shaft 24 and the inside of nipple 29.

Housing 19 has a tangential outlet 31 from space 23. The rotators 16,17, together with tubular shaft 24, are driven in rotation by a driveshaft 33 journaled through bearing 34 in the wall of housing 19.Rotation of tubular shaft 24 in a clockwise direction as shown in FIG. 2causes rotation of blood or other fluid passing inwardly through inletpipe or conduit 37 which is sealed to tubular shaft 24 by O-ring 38disposed in suitable ring grooves inside of tubular shaft 24 and aroundthe exterior of conduit 37.

The blood, or other fluids to be pumped are passed in through conduit 37from which the fluid passes into the interior of tubular shaft 24, thenradially outwardly through circular openings 27, 28 in the sides oftubular shaft 24. The fluid is propelled in rotation by rotation ofshaft 24 and by rotation of the two spaced rotators 16, 17. Therotational velocity of the fluid increases as the radial movement of thefluid outwardly progresses. In other words, fluid rotating at the outeredges of rotators 16, 17 is in faster rotation than is fluid rotating atthe inner edges of the rotators. The shapes of rotators 16, 17 are suchthat the outward fluid flow volume is constant from the inner edges ofthe rotators to the outer peripheries of the rotators. The rotators arecloser together at their peripheries such that the volume of outwardlyflowing fluid per units of time at the periphery is the same as thevolume of outwardly flowing fluid per unit of time at any circle inwardof the rotator peripheries.

In the drawings, the equipment shown is schematic and not to scale, theoutward convergence of the rotators actually being considerably greaterthan shown, with the rotators being closer together at their outer edgesor peripheries, and with the flow as described in the preceedingparagraph.

As will be apparent, rotation of the rotators in a clockwise direction,as depicted in FIG. 2, causes the fluid to rotate in constantlyincreasing circular paths from shaft 24 to the space 23 around the outeredges of the rotators from which the fluid exits from tangential outlet31.

Referring now to FIGS. 3 and 4 ofthe drawings, there is shown a pumpwherein the rotators are curved, i.e., dish-shaped, the curves of therotators being such that the spacing therebetween diminishes outwardlyso that the outward flow rate at constantly increasing speed isvolume-constant. Fluid flows from an inlet conduit 43 into the spacebetween rotators 44, 45, each of curved shape with closer spacing towardthe rotator edges. The rotators terminate at the same plane, toward theright, as the rotators are shown in FIG. 3. The rotators areconnected-by plural connector rods 47 of streamline shape as shown inFIG. 4. The rotators are driven in rotation, clockwise as shown in FIG.4, by drive means connected to shaft 49 which is carried by rotator 45.The inner edge of rotator 44 is sealed to conduit 43 by O-ring seal 52.The pump housing is integral with (or sealed with) the inlet conduit 43at 53, the housing being referred to by reference numeral 56. Thehousing has curved walls 57, 58 which are closely spaced from and are ofthe same curvatures as rotators 44, 45, respectively. The rotator edgesare sealed to the housing walls by O-ring seals 61, 62. An annularcirculation chamber 64 is provided within the housing beyond the ends ofthe rotators. An outlet 65 is provided therefrom through which pumpedfluid emerges.

The inner face of rotator 45 is provided with a pointed raised formation67 which serves to smooth flow from conduit 43 to the space between therotators. Streamline laminar flow is achieved through conduit 43, bysuitable relatively low flow rates therethrough, and the laminar flow ispreserved during flow through the space between the rotators. and therotator rotation is at a speed such that the rotators impel fluidstherebetween in laminar-flow rotation, at continuously increasing speedsas the fluids move outwardly between the rotators toward outlet 65. Thetwo housing parts are connected at bolt flanges 57a, 58a. A bearing 69is provided about drive shaft 49 and housing 56 whereby the rotators maybe easily driven in rotation in the prescribed manner.

Referring now to FIG. 5 of the drawings, a modified form ofpump is shownwherein the rotators are each of hollow frusto-conical form. Rotators71, 72 are connected by plural connector bars 73 of streamlined form, asshown for bars 47 in FIG. 4, so that the two rotators are driven inrotation together by rotational energies provided through shaft 75 froma suitable drive means (not shown). The housing 77 is conforminglyshaped, with angular walls 78, 79 of conical shape corresponding to theangles of the respective rotators 71, 72. Rotator 71 has a nipple-shapedend 81 which is fitted within an outwardly upset opening of the housingadjacent the end of inlet conduit 82 which is formed integrally with thehousing. The housing parts are joined at bolting flanges 78a, 79a.

Bearing 84 is disposed around shaft 75 to reduce fric tion of rotation.An angular outlet 86 is provided from the housing adjacent space 87disposed annularly beyond the rotator edges. The conical angles of therotator surfaces, facing one another, are such that the space is reducedoutwardly from the rotator centers such that, at least approximately,the volume movement of fluid through the pump is constant at each radialextent of the rotators.

In FIG. 6, the pump shown has plural rotators 9194, conical and atdifferent angles, so that the rotators are convergent toward theirperipheries. Housing 97 is shaped to conform with the shapes of theouter rotators, and has entrance upset 98 to receive rotator 91 nipple99 sealed by O-ring 100. Shaft 102 is journaled for rotation throughbearing 103. The rotators are joined by bars 104. The housing parts areconnected at flange connection 106. Housing 97 has tangential fluidoutlet 108 from annular circulation space 110.

In the FIG. 6 embodiment of apparatus, the inner edges of rotators 92,93 are flared toward the inlet 112, such that approximately the samevolume of fluid will enter from the inlet to the three spaces betweenrotators.

Referring to FIG. 7, there is shown a rotator arrangement wherein thepair of rotators 114, are double curved between their centers andperipheries, the rota tors being convergent as before to achieve uniformvolume flow at all radial extents of the rotators.

Referring to FIG. 8, there is shown a pump the design of whicheliminates the use of seals between the rotators and housing. Thehousing consists of two parts. Housing part 151 is flaringly enlargedfrom end 152 around fluid inlet 153 and has a flat surface 154 aroundits outer edge to receive a ring-shaped clamp nut 155 thereagainst. Nut155 extends beyond the end of the housing and is internally threaded.Housing part 157 is outwardly cylindrical and has threads at its openend onto which nut 155 is screwed to connect housing parts 151, 157together. A seal 158 is disposed in a groove around the annular end ofhousing part 151 to make the connection leakproof.

A tangential outlet port 159 is provided from the sidewall of housingpart 157. At the center of the closed end 161 of housing part 157, anopening is provided to receive shaft 162, journaled in bearing 163, andsurrounded by seal 164, the bearing and seal are disposed in annularenlargements around the shaft opening.

Endwall 161 is inwardly thickened toward its center. The inner end ofshaft 162 is of conical shape, and a plurality, preferably three,small-diameter rods166 depend angularly from the shaft end at equalangles and equally spaced. A plurality of accelerators of rotators168-171 of differentflared curvatures are supported by the rods 166. Therotators 168-171 have holes therethrough to receive the rods 166,rotator 168 being positioned at the ends of the rods, and rotators169-171 being spaced between rotator 168 and the end of shaft 162. Therotators are fixed to the rods by pressfitting, or by any other suitablemeans.

The rotators 168-171 have circular center openings 168a-171a ofsequentially smaller size. The spacing between the centers of rotators168, 169 is larger than the spacing between rotators 169, 170, which islarger than the spacing between rotators 170, 171. Rotator 168 is spacedfrom the inside of the flared wall of housing part 151, and rotator 171is spaced from the flared inside surface of end wall 161 of housing part157.

The between-the-rotator spacings decrease outwardly as in the otherembodiments. However, the spacings between the walls of the housing andend rotators, rotators 168'and 171, increase outwardly. The reason forthis is that, because the housing walls do not rotate, and because theangular rotator and fluid speeds increase outwardly, the shear on thefluid would increase outwardly if the end spacings were uniform ordecreased outwardly. Therefore, in order to avoid increased shear on thefluid as it circulates outwardly to the rotator peripheries, the endrotator-housing spacings are increased outwardly.

As fluid flows in through inlet 153, the fluid is reduced in volume asit moves toward the right, as shown in FIG. 8. The rotator centeropenings 168a-171a are sized to receive the remaining flow at laterrotators after partial flow has been diverted by earlier rotators. Theunequal inner periphery spacings of the rotators are required by themore sharply flared shapes of earlier rotators as compared with laterrotators.

The rotators 121, 122, of FIG. 9 are joined by plural circularly spacedbars 123, and are of flaring curved shapes toward their outer ends. Thehousing parts 124, 125 are joined at bolting flanges 126, 127. O-ringseals are provided at 128, 129, 130. Rotator 122 is mounted on the endof rotating shaft 131, exterior drive means being provided therefor. Thepumped fluid exits from between the rotators to a space radially outwardof the rotator edges to exit through tangential port 133.

in FIG. 10, the pump structure is similar to that shown in FIG. 9. Thepump has rotators 136, 137 connected by bars 138, as housing made up ofparts 140, 141, seals 143-145, and outlet port 146. The fluid exitingfrom between the rotators exits to a space beyond the rotator edges inan axial direction.

It will be seen that the blood or other fluid passing through the pumpsis not submitted to any substantial agitation by the rotation of therotators, of whichever form, or by any other portion of the pumpapparatus. There are no sudden changes in direction of the flow throughthe pump, all joints between surfaces being smooth and all surfaces overwhich the fluid flows being smooth.

The spacings between the outer peripheral edges of the rotators may bevery close, i.e., a few thousandths of an inch, or may be larger.inwardly of the rotator outer edges, the spacings become increasinglylarger. Close peripheral spacings do not cause unacceptable trauma toblood but do enable the pump to work efficiently. The efficiency of thepump is directly related to the transfer efficiency of the rotatorswhich is a function of the rotator spacing. There exists an optimumspacing for each set of rotators. Therefore, by using the optimumspacing, it is possible to optimize the pump efficiency. However, if theclose spacings are maintained over a considerable radial extent, thenexcessive trauma to blood does occur. However, the majority of thespacing effect on efficiency takes place at the largest radii. Thusclosespacing need only be maintained at the periphery. Therefore, therotators can be made with the continuously outwardly decreasing spacingsas herein described and thus low traumaticity and high efficiency can bemaintained.

It will be realized that pumps may be supplied according to theinvention with any number of pumping stages, and may include individualpumping stages of any of the types mentioned herein in any combination.

in each of the pumps shown in FIGS. 1-6, and pumps wherein use is madeof rotators (or accelerators) of the different forms shown in FIGS. 7-8,it will be noted that the rotators are designed to avoid turbulence andto avoid rapid pressuring and depressuring of the blood or other fluidbeing pumped, and also to avoid any physical grinding or abrasive actionupon the fluid. As has been made clear, these rotator designs are madein this manner in order that blood or other delicate liquids or gasesbeing pumped, some containing solids in suspension, will not sufferdetriment and will not be destroyed by the pumping operation.

The convergence of the rotators, with diminution of the flow spacetherebetween outwardly, prevents cavitation (dissolved gases coming outof solution to form bubbles because of the pressure reduction within thepumps), which would adversely affect pumping efficiencies and causedamage to certain fluids, such as blood. The convergence of the rotatorsmay be such that the flow rate either somewhat increases outwardly orsomewhat decreases outwardly, with corresponding pressure changes on thefluid being pumped. In the outer annular flow spaces between therotators mximum fluid velocity is maintained, so that conversionofvelocity to pressure occurs at the outer pump housing and as fluidenters the pump outlet.

ln'contrast to centrifugal pumps, the revolutions per minute of therotators employed with the pumps herein shown and described are designedto be kept minimal. The several rotator designs presented are each of aform adapted to progressively increase the circular fluid velocities asthe rotator turns and as the fluid advances toward the periphery of therotator. In each pump presented, the annular fluid circulation space isalmost entirely unobstructed and regular so that fluid can circulatetherein without turbulence or baffle effects. The connecting struts,which are kept as small as possible, provide the only exception to this.These struts may also be kept as close to the center of rotation aspossible to minimize their velocities, as shown in FIG. 8.

As hereinbefore indicated, pumps may be made according to the inventionincorporating features from one or more of the preferred embodimentsshown and described herein, any particular feature not being confined touse only with the other features in connection with which it is hereinshown and described.

The pumps and their parts may be constructed of any materials compatiblewith their intended use, including metals, mineral materials, plastics,rubbers, wood, or other suitable materials. When blood is to be pumped,consideration must be given to biological compatibility so that traumato the blood will not result. Low temperature isotropic carbon andcertain polymers or rubbers have been successfully used in contact withblood, without traumatic effects, and may be used in construction of thepumps for blood pumping adaptations. Noncorrosive metals and alloys maybe used in the pumps where required.

The housings and rotators may be constructed of suitable material sothat the housing may be rigid, semirigid, or elastic in whole or inpart. The non-rigid constructions can be used for imparting pulseconfigurations to blood in heart simulation pumps.

While the rotators shown herein may in some cases perform better whenrotated in one direction, it should be understood that they may berotated in either direction, or may vary in rotational velocity anddirection, i.e., reversed, without other modification of the pumps. Eachof the rotators presents surfaces to the fluid being pumped, to causeaccelerating circular fluid motion in the pumping chamber. In somecases, the surfaces are parallel to the fluid flow; in other casesparallel and non-parallel surfaces are provided. Each of these surfaces,of whatever form, will accelerate the fluid re.- gardless of thedirection of rotation of the rotator. Each rotator should be rotated ata speed such that essentially no fluid turbulence occurs, anddifferences in the rotator designs affects the maximum speed at which aparticular rotator may be rotated. The physical and flow properties ofthe fluid pumped will, of course, also affect the maximum speeds ofrotation at which the rotators may be operated without turbulence andother objectionable effects, such as cavitation, vapor binding,

and the like. It is, therefore, not possible to set forth exactrotational speed ranges for the rotators. But, the speeds of rotationwill usually be substantially lower than those of traditionalcentrifugal pumps and blowers, wherein turbulence always occurs as theimpellers thrust the fluid radially outwardly against the periphery ofthe pumping chamber, and those of the aforementioned multiple disc pumpsand compressors. To the end of achieving reduced rotator speeds, pumpsprovided according to this invention may be of larger size than otherpumps, for the same pumping capacity. As internally placed heart pumps,the pumps may be as large as four inches in diameter, and, with removalof a lung, for example, even larger.

According to the precepts ofthis invention, the forms of the rotatorsmay vary considerably. For example, the

rotators may be constructed entirely or partly of porous or perforatematerials, i.e., the rotators which accelerate the fluid circularly maybe made of screen, of perforate plates or sheets, of spaced rods, or thelike, and will still ably perform their fluid accelerating function.They may also be constructed out of solid or nonporous materials.Rotators may be of axially extended form, so that the fluid isaccelerated axially or axially and radially. Designs of this naturewould extend the flowpath from inlet to outlet so that accelerationwould be at a slower rate. The rotators of FIGS. 1-7 and 8-10 are madeto become closer together, instead of farther apart, toward theperiphery of the rotator. in each of the pumps shown and/or described,one or more tangential outlets could be provided, disposed in thedirection of fluid flow inside the peripheral wall of the pump. inmulti-stage pumps, the several rotators, which may be alike or unlike,may be driven at different rotational speeds. The axes of multi-stagerotators may be offset and in other positions out of alignment.

While preferred embodiments of apparatus according to the invention havebeen shown and described, many modifications thereof may be made by aperson skilled in the art without departing from the spirit of theinvention, and it is intended to protect by Letters Patent all forms ofthe invention falling within the scope of the following claims.

What is claimed is:

l. A method of pumping blood which is subject to damage under impact andshear, said method comprising rotating an impeller having a pair ofaxially spaced smooth discs that define a constant annular crosssectional vaneless pumping chamber therebetween, providing one disc witha central opening communicating with the inner portion of said annularpumping chamber, subjecting the blood to centrifugal action byengagement with the smooth walls of the rotating discs that define thepumping chamber, increasing the outward movement of blood under laminarflow conditions without appreciable turbulance to the outer peripheriesof the discs and collecting the discharged laminar flow of said bloodfrom said pumping chamber in an annular unobstructed chamber about saiddiscs' without subjecting the blood to impact and/or shear.

2. A method according to claim 1 wherein the discs converge outward oftheir centers.

3. A method according to claim 1 wherein the outer portion ofthe pumpingchamber is spaced axially of the inner portion of the pumping chamber.

4. A method of pumping natural and artificial fluids which are subjectto damage under impact and shear, said method comprising rotating animpeller having a pair of axially spaced smooth discs that define aconstant annular cross sectional vaneless pumping chamber therebetween,providing one disc with a central opening communicating with the innerportion of said annular pumping chamber, subjecting the fluid tocentrifugal action by engagement with the smooth walls of the rotatingdiscs that define the pumping chamber, increasing the outward movementof fluid under laminar flow conditions without appreciable turbulance tothe outer peripheries of the discs and collecting the discharged laminarflow of said fluid from said pumping chamber in an annular unobstructedfluid from said pumping chamber in an annular unobstructed chamber aboutsaid discs without subjecting the fluid to impact and/or shear.

5. A method according to claim 4 wherein the discs converge outward oftheir centers.

6. A method according to claim 4 wherein the outer portion of thepumping chamber is spaced axially of the inner portion of the pumpingchamber.

7. A method of pumping blood which is subject to damage under impact andshear, said method comprising rotating an impeller having a plurality ofaxially spaced smooth discs that define constant annular cross sectionalvaneless pumping chambers therebetween, providing all but the axiallyrearmost of the discs with central openings communicating with the innerportions of said annular pumping chambers, subjecting the blood tocentrifugal action by engagement with the smooth walls of the rotatingdiscs that define the pumping chambers, increasing the outward movementof blood under laminar flow conditions without appreciable turbulance tothe outer peripheries of the discs and collecting the discharged laminarflow of said blood from said pumping chambers in an annular unobstructedchamber about said discs without subjecting the blood to impact and/orshear.

8. A method according to claim 7 wherein the discs converge outward oftheir centers.

9. A method according to claim 7 wherein the outer 12 portion of eachpumping chamber is spaced axially of its inner portion.

10. A method of pumping natural and artificial fluids which are subjectto damage under impact and shear, said method comprising rotating animpeller having a plurality of axially spaced smooth discs that defineconstant annular cross sectional vaneless pumping chambers therebetween,providing all but the axially rearmost of the discs with centralopenings communicating with the inner portions of said annular pumpingchambers, subjecting the fluid to centrifugal action by engagement withthe smooth walls of the rotating discs that define the pumping chambers.increasing the outward movement of fluid under laminar flow conditionswithout appreciable turbulance to the outer peripheries of the discs andcollecting the discharged laminar flow of said fluid from said pumpingchambers in an annular unobstructed chamber about said discs withhoutsubjecting the fluid to impact and/or shear.

1]. A method according to claim 10 wherein the discs converge outward oftheir centers.

12. A method according to claim 10 wherein the outer portion of eachpumping chamber is spaced axi-

1. A method of pumping blood which is subject to damage under impact andshear, said method comprising rotating an impeller having a pair ofaxially spaced smooth discs that define a constant annular crosssectional vaneless pumping chamber therebetween, providing one disc witha central opening communicating with the inner portion of said annularpumping chamber, subjecting the blood to centrifugal action byengagement with the smooth walls of the rotating discs that define thepumping chamber, increasing the outward movement of blood under laminarflow conditions without appreciable turbulance to the outer peripheriesof the discs and collecting the discharged laminar flow of said bloodfrom said pumping chamber in an annular unobstructed chamber about saiddiscs without subjecting the blood to impact and/or shear.
 2. A methodaccording to claim 1 wherein the discs converge outward of theircenters.
 3. A method according to claim 1 wherein the outer portion ofthe pumping chamber is spaced axially of the inner portion of thepumping chamber.
 4. A method of pumping natural and artificial fluidswhich are subject to damage under impact and shear, said methodcomprising rotating an impeller having a pair of axially spaced smoothdiscs that define a constant annular cross sectional vaneless pumpingchamber therebetween, providing one disc with a central openingcommunicating with the inner portion of said annular pumping chamber,subjecting the fluid to centrifugal action by engagement with the smoothwalls of the rotating discs that defiNe the pumping chamber, increasingthe outward movement of fluid under laminar flow conditions withoutappreciable turbulance to the outer peripheries of the discs andcollecting the discharged laminar flow of said fluid from said pumpingchamber in an annular unobstructed fluid from said pumping chamber in anannular unobstructed chamber about said discs without subjecting thefluid to impact and/or shear.
 5. A method according to claim 4 whereinthe discs converge outward of their centers.
 6. A method according toclaim 4 wherein the outer portion of the pumping chamber is spacedaxially of the inner portion of the pumping chamber.
 7. A method ofpumping blood which is subject to damage under impact and shear, saidmethod comprising rotating an impeller having a plurality of axiallyspaced smooth discs that define constant annular cross sectionalvaneless pumping chambers therebetween, providing all but the axiallyrearmost of the discs with central openings communicating with the innerportions of said annular pumping chambers, subjecting the blood tocentrifugal action by engagement with the smooth walls of the rotatingdiscs that define the pumping chambers, increasing the outward movementof blood under laminar flow conditions without appreciable turbulance tothe outer peripheries of the discs and collecting the discharged laminarflow of said blood from said pumping chambers in an annular unobstructedchamber about said discs without subjecting the blood to impact and/orshear.
 8. A method according to claim 7 wherein the discs convergeoutward of their centers.
 9. A method according to claim 7 wherein theouter portion of each pumping chamber is spaced axially of its innerportion.
 10. A method of pumping natural and artificial fluids which aresubject to damage under impact and shear, said method comprisingrotating an impeller having a plurality of axially spaced smooth discsthat define constant annular cross sectional vaneless pumping chamberstherebetween, providing all but the axially rearmost of the discs withcentral openings communicating with the inner portions of said annularpumping chambers, subjecting the fluid to centrifugal action byengagement with the smooth walls of the rotating discs that define thepumping chambers, increasing the outward movement of fluid under laminarflow conditions without appreciable turbulance to the outer peripheriesof the discs and collecting the discharged laminar flow of said fluidfrom said pumping chambers in an annular unobstructed chamber about saiddiscs withhout subjecting the fluid to impact and/or shear.
 11. A methodaccording to claim 10 wherein the discs converge outward of theircenters.
 12. A method according to claim 10 wherein the outer portion ofeach pumping chamber is spaced axially of its inner portion.